how can I fix wordpress problem Forbidden You don't have permission to access /wp- login.php on this server.

dedeuc:
how can I fix wordpress problem Forbidden
You don't have permission to access /wp-
login.php on this server.

What actually was the last thing you did before you encountered this problem?
Over 98% of the time, this is often caused due to .htaccess or permissions or you may be getting a mod_security error.

Did you recently activate a security plugin, maybe too many failed log in attempts from your IP?

I believe you should have access to your web host CPanel. Just login and try temporarily disabling your .htaccess or add the following lines to it
<IfModule mod_security.c>
SecFilterEngine Off
SecFilterScanPOST Off
</IfModule>

OR

Look for and trying removing the following lines if you can find it

<FilesMatch "^(xmlrpc\.php|wp-trackback\.php|wp-login\.php|admin\.php)">
Order Deny,Allow
Deny from all
Allow from 111.111.111.111
</FilesMatch>

Hope that helps